Question: Solve for $x$ and $y$ using substitution. ${2x+y = 5}$ ${x = -5y-2}$
Since $x$ has already been solved for, substitute $-5y-2$ for $x$ in the first equation. ${2}{(-5y-2)}{+ y = 5}$ Simplify and solve for $y$ $-10y-4 + y = 5$ $-9y-4 = 5$ $-9y-4{+4} = 5{+4}$ $-9y = 9$ $\dfrac{-9y}{{-9}} = \dfrac{9}{{-9}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = -5y-2}\thinspace$ to find $x$ ${x = -5}{(-1)}{ - 2}$ $x = 5 - 2$ ${x = 3}$ You can also plug ${y = -1}$ into $\thinspace {2x+y = 5}\thinspace$ and get the same answer for $x$ : ${2x + }{(-1)}{= 5}$ ${x = 3}$